This application requests five-years of support for a longitudinal study of obstructive sleep apnea (OSA). In work conducted to date, cross-sectional information has been collected from 215 families of which 106 had a proband with OSA and 65 were ascertained as neighbor controls. In total, the population numbers over 1,100 persons. A wide array of information has been collected including an in-home polysomnogram, detailed questionnaire information, pulmonary function testing, anthropometry and cephalometry, and blood pressure. More intense data collection for samples of subjects has been carried out for airway structure and ventilatory control. A number of methodologic studies have been undertaken in support of the project. Among the many findings to date are a demonstration of familial aggregation of OSA and associations of OSA with abnormal ventilatory control and a suggestion of differences in the picture of OSA in blacks and whites. A broad set of activities is planned for the five years of this application. The cohort will be expanded by the addition of 85 families identified through an affected proband, leading to a total of 300 families. These new cohort members will be characterized in the fashion similar to that previously used. Follow-up will be conducted on those initially recruited for apnea levels, blood pressure, body fat distribution, cranial facial dimensions, pulmonary function, and other factors of interest. For 450 of the individuals, follow- up will extend through nine years. A nested case-control study is also proposed that will include 24-hour ambulatory blood pressure monitoring and echocardiography. A principal analytic tool will be variance component modeling.